The MBTA is moving closer to disposing of its North Station parking garage – a move that could spur millions of square feet in new commercial development along Causeway Street in Boston – while continuing to insist that it doesn’t have to dump the garage at all.

The North Station garage is an anomaly in the T’s extensive parking network because it sits downtown, at the end of a mass transit line. The debt-wracked transportation agency wound up with ownership of the 1,280-space garage in 1993, as part of a complex deal with the city of Boston, former Senate President William Bulger and Delaware North, owners of the then yet-to-be-built Fleet Center that would replace the aging Boston Garden. That deal allowed the T to run the old elevated Green Line through two levels of the garage, and to extend northbound commuter rail tracks onto the garage’s roof. The structure serves as the foundation of today’s TD Garden.

Last year, the state Legislature passed a massive bill that consolidated the state’s sprawling transportation bureaucracy. Language buried deep in that bill authorized the T to sell the North Station garage to a user that would spur economic development in the neighborhood.

Cash Cow

The T has long said the North Station garage isn’t a core asset. Still, the agency has been reticent to part with the garage because it is, simply, a cash cow. In 2008, the garage netted $4.9 million for the T.

Delaware North has had a longstanding interest in purchasing the garage under the Garden, and has been unsuccessful in those efforts, thanks largely to the fat income stream it provides.

The quasi-public agency doesn’t pay taxes or insurance, and its utility costs are paid in bulk; all of that means the garage is more valuable to the T than a private operator because the T’s margins are fatter.

But in recent years, the T’s debt load has exploded, and its ability to service that debt is strained by falling revenues. The agency and the state have also said publicly that they covet the United States Postal Service’s South Station Postal Annex, a 16-acre facility that could be the staging ground for a dramatic expansion of South Station rail service. But Beacon Hill observers have said the state will have little tolerance for taking on the Postal Annex without raising cash through asset sales first.

“What we’re struggling with is, the garage generates a significant amount of money for the T,” said Mark Boyle, the T’s director of real estate. “The T has over $4 billion in debt. We’re struggling with analyzing whether selling the garage to pay down the debt is more advantageous than [taking an] annual profit.”

So Close, But So Far

All of that means the North Station garage is closer than it’s ever been to landing in private hands. The T’s real estate consultant, Transit Realty Assoc., recently asked developers and parking operators to submit letters of interest. And last week, the T and Transit Realty hosted an informal meeting of interested parties at the State Transportation Building in Park Square.

“There is momentum to make a decision rather quickly,” said Gregory Dicovitsky, Transit Realty’s project manager on the garage sale. Speaking at last week’s meeting, Dicovitsky said the T has not decided whether to sell the garage outright, lease it long-term or enter a public-private partnership.

“We’re looking at what preferred business models might be applicable here,” he said. Based on input from interested bidders, the T hopes to issue a request for proposals in September, and designate a winning bidder in November.

At the same time, Dicovitsky insisted, “The T is not required to sell or lease the garage.”

Delaware North’s presence around the North Station garage appears to complicate matters for potential bidders. Current zoning allows the company to build up to 1.7 million square feet in commercial space on the site of the old Garden. That development would be supported by a new 800-space underground garage.

Delaware North has easements, dating to 1993, to punch holes in the North Station garage’s southern wall to access its future garage, and to use the old garage’s ramps and entrances.

Observers said they believe Delaware North might end up being the only bidder – a fact that could derail the sale altogether, since the garage is worth more to the T than it is to anyone else.